Some doctors suggest that vinegar will ____ people from being infected ___ H1N1.

English is difficult _______interesting.

This morning your mobile phone was alwaysbusy. I couldn’t ________ to you until several attempts.—Oh, I’m sorry. I was discussing the priceof our products with a client over the phone.

_____ do you go to the zoo —Seldom.

________ the jewels were locked in a strong box，the thieves stole them without any difficulty